Electromagnetic interference shielding filter and manufacturing method thereof

ABSTRACT

An electromagnetic interference (EMI) shielding filter includes a conductive pattern for shielding electromagnetic waves; and blackened layers formed on a surface of the conductive pattern. The electromagnetic interference (EMI) shielding filter is manufactured by preparing a base film; forming on the base film a first blackened layer, a conductive layer, and a second blackened layer in sequence; and patterning the first blackened layer, the conductive layer, and the second blackened layer by using a same mask, and forming on front and rear surfaces of an EMI shielding layer a conductive pattern comprising the first and second blackened layers.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an electromagnetic interferenceshielding filter and a manufacturing method thereof, in which thesurface of an electromagnetic interference shielding layer is melanized(or blackened) to improve contrast ratio.

2. Discussion of the Background Art

In general, image display devices have an electromagnetic interference(EMI) shielding filter on the front surface to shield emission ofelectromagnetic waves to outside. The EMI filters not only shieldelectromagnetic waves but also transmit visible rays, so they usuallyhave a conductive mesh pattern. A related art conductive mesh pattern,however, reflected an external light or a visible ray from a displaypanel. As a result, contrast was deteriorated. This problem is apparentin a plasma display panel (hereinafter it is referred to as “PDP”) thatdisplays images by using a gas discharge.

PDPs regulate gas discharge time of each pixel on the basis of digitalvideo data, and display an image. Typical examples of these PDPs are ACPDPS, as shown in FIG. 1, which includes three electrodes and are drivenby an AC voltage.

FIG. 1 is a perspective view of a related art AC PDP. More particularly,FIG. 1 illustrates the structure of a discharge cell corresponding to asub-pixel.

As shown in FIG. 1, the discharge cell is divided into an upper plate 15and a lower plate 25. The upper plate 15 includes an upper substrate 10where a sustain electrode pair 12A and 12B, an upper dielectric layer14, and a protective film 16 are formed in sequence. The lower plate 25includes a lower substrate 18 where an address electrode 20, a lowerdielectric layer 22, a barrier rib 24, and fluorescent layers 26.

The upper substrate 10 and the lower substrate 18 are spaced out inparallel by the barrier rib 24. The sustain electrode pair 12A and 12Brespectively includes a transparent electrode for transmitting visiblerays, and a metal electrode for compensating resistance of thetransparent electrode. The transparent electrode is relatively widerthan the metal electrode. The sustain electrode pair 12A and 12Bincludes a scan electrode 12A and a sustain electrode 12B. The scanelectrode 12A provides scan signals for determining data supply time,and sustain signals for sustaining the gas discharge. On the other hand,the sustain electrode 12B mainly provides sustain signals for sustainingthe discharge. The upper dielectric layer 14 and the lower dielectriclayer 22 are piled up with charges from the gas discharge. Theprotective film 16 protects the upper dielectric layer 14 from damagescaused by a sputtering of plasma and thus, extends lifespan of the PDPand improves the emission efficiency of secondary electrons. Theprotective film 16 is usually made from magnesium oxide NgO). Thedielectric layers 14 and 22 and the protective film 16 lower anexternally applied discharge voltage. The address electrode 20 is formedat tight angles to the sustain electrode pair 12A and 12B. The addresselectrode 20 provides data signals for selecting cells to be displayed.The barrier rib 24 together with the upper and lower substrates 10 and18 create a discharge space. The barrier rib 24 is formed in parallelwith the address electrode 20, and prevents ultraviolet rays generatedby the gas discharge from being leaked to the adjacent discharge cells.The fluorescent layer 26 is applied to the surface of the lowerdielectric layer 22 and barrier rib 24, and generate one of visible raysin red, blue, or blue. The discharge space is filled with differentcompositions of inert gas mixtures including He, Ne, Ar, Xe, and Kr, orExcimer gas for generating ultraviolet rays.

Thusly structured discharge cell is selected by an opposing electrodedischarge between the address electrode 20 and the scan electrode 12A,and sustained by a surface discharge between the scan electrode 12A andthe sustain electrode 12B. Therefore, the fluorescent layer 26 isexcited by ultraviolet rays generated during the sustain discharge, andvisible rays are emitted to the outside of the cell. In this case, thedischarge cell controls the cell's discharge sustain period, namelyfrequency of the sustain discharge, according to video data, and emits alight at a gray scale level.

FIG. 2 is a schematic perspective view of a PDP set including the PDP 30of FIG. 1.

As shown in FIG. 2, the PDP set includes a case 60, a printed circuitboard 50 (hereinafter, it is referred to as (“PCB”) housed in the case60, a PDP 30, a glass type front filter 40, and a cover 70 connected tothe case 60 and encompassing the glass type front filter 40.

As discussed before with reference to FIG. 1, the PDP 30 includes anupper plate 15 and a lower plate 25 connected to the upper plate 15.

The PCB 50 disposed on the rear surface of the PDP 30 includes aplurality of driving and control circuits for driving the sustainelectrode pair 12A and 12B and the address electrode 20 formed on thePDP 30. Situate between the PCB 50 and the PDP 30 is a heat radiationplate (not shown) for radiating heat emitted from the PDP 30 and the PCB50.

The glass type front filter 40 shields electromagnetic waves generatedfrom the PDP 30 towards the front surface, prevents external lightreflection, blocks near-infrared rays, and corrects colors. To this end,the glass type front filter 40 includes, as shown in FIG. 3, a firstantireflection coating 44 attached to a front surface of a glasssubstrate 42, an EMI shielding filter 46, a NIR (near infrared ray)blocking film 48, a color correcting film 52, and a secondantireflection coating 54, the EMI shielding film 46, the NIR blockingfilm 48, the color correcting film 52 and the second antireflectioncoating 54 being layered in cited order on the rear surface of the glasssubstrate 42.

The glass substrate 42 is made from a reinforced glass to support theglass type front filter 40 and to protect the front filter 42 and thePDP 30 from damages caused by external impacts. The first and secondantireflection coatings 44 and 54 prevent incident light rays fromoutside from being reflected back to the outside and thus, improvecontrast effects. The EMI shielding filter 46 absorbs electromagneticwaves generated from the PDP 30, and shields the emission of theelectromagnetic waves to outside. The NIR blocking film 48 absorbs nearinfrared rays at a wavelength band of 800-1000 nm that are generatedfrom the PDP 30, and blocks the emission of the near infrared rays tooutside. This is how infrared rays (approximately 947 nm) generated froma remote controller are normally input to an infrared ray receiver builtin the PDP set. The color correcting film 52 contains a color dye, whichis used to adjust or correct colors, whereby color purity can beimproved. These films 44, 46, 48, 52, and 54 are adhered to the glasssubstrate 42 through an adhesive or glue.

The case 60 protects the PCB 50, the glass type front filter 40 and thePDP 30 from external shocks, and shields electromagnetic waves emittedfrom side and rear surfaces of the PDP 30. Also, to ensure that theglass type front filter 40 is separated from the PDP 30, the case 60 iselectrically connected to the EMI shielding filter 46 of the glass typefront filter 40 through a support member (not shown) that supports fromthe rear surface of the case 60. Therefore, the case 60 and the EMIshielding filter 46 of the glass type front filter 40 are both earthedto a ground voltage, and absorb electromagnetic waves emitted from thePDP 30 and discharge them. This is how the emission of theelectromagnetic waves to outside is blocked.

Lastly, the cover 70 encompasses the outside of the glass type frontfilter 40, and is connected to the case 60.

As discussed above, the related art PDP set includes the glass typefront filter 40 for shielding electromagnetic waves and correctingoptical characteristics. However, because the glass type front filter 40includes a glass substrate made from the reinforced glass, which isrelatively thick, the thickness and weight of the PDP set wereincreased, and the cost of manufacture was also increased.

As an attempt to solve the above-described problems, a film type frontfilter without a glass substrate, as shown in FIG. 4, has beensuggested. The film type front filter 65 shown in FIG. 4 includes acolor correcting film 68, a NIR blocking film 66, an EMI shieldingfilter 64, and an antireflection layer 62, each being sequentiallyadhered to an upper plate 15 of the PDP 30.

The antireflection coating 62 prevents incident light rays from outsidefrom being reflected back to the outside. The EMI shielding filter 64absorbs electromagnetic waves generated from the PDP 30, and shields theemission of the electromagnetic waves to outside. The NIR blocking film66 absorbs near infrared rays that are generated from the PDP 30, andblocks the emission of the near infrared rays to outside. The colorcorrecting film 68 contains a color dye, which is used to adjust orcorrect colors, whereby color purity can be improved. These films 62,64, 66, and 68 are adhered to the PDP 30 through an adhesive or glue.

Both the glass type front filter 40 of FIG. 3 and the film type frontfilter 65 include an EMI shielding filter 46 or 64 for shielding EMIfrom the PDP 30. As shown in FIGS. 5 and 6, the EMI filter 46 or 64includes an EMI shielding layer 75 formed of conductive meshes 74 andframes 72 for supporting the conductive meshes 74, and a base film 75formed on the EMI shielding layer 75.

Referring to FIGS. 5 and 6, to form the conductive meshes 74 and theframes 72 a metal layer made from silver (Ag) or copper (Cu) for exampleundergoes photolithography and etching processes to be patterned. To bemore specific, a metal foil is formed on the base film 76, and the metalfoil is coated with a photoresist. Later, the photoresist coating ispatterned by using a mask and thus, the frame and a photoresist patternin mesh type are formed. The metal foil is patterned by using thephotoresist pattern as a mask, and as a result, the EMI shielding layer75 including the frames 72 and the conductive meshes 74 is formed on thebase film 76, as illustrated in FIG. 6. Any photoresist patternsremaining on the frames 72 and the conductive meshes 74 are removedthrough a strip process.

The EMI shielding layer 75, namely the conductive meshes 74 and theframes 72, of the related art EMI shielding filter 46 or 64 is usuallymade from highly lustrous metals. Thus, an externally incident lights R1or display lights R2 emitted from the PDP 30 are reflected by themetallic conductive meshes 74 and frames 72. These reflected lights bythe EMI shielding filter 75 increases overall black level or brightnessof the PDP 30, resulting in deterioration of contrast ratio.

SUMMARY OF THE INVENTION

An object of the invention is to solve at least the above problemsand/or disadvantages and to provide at least the advantages describedhereinafter.

Accordingly, one object of the present invention is to solve theforegoing problems by providing an electromagnetic interferenceshielding filter and a manufacturing method thereof, in which thesurface of an electromagnetic interference shielding layer is melanized(or blackened) to improve contrast ratio.

The foregoing and other objects and advantages are realized by providingan electromagnetic interference (EMI) shielding filter, including: aconductive pattern for shielding electromagnetic waves; and blackenedlayers formed on a surface of the conductive pattern.

Another aspect of the invention provides a manufacturing method of anelectromagnetic interference (EMI) shielding filter, the methodincluding the steps of preparing a base film; forming on the base film afirst blackened layer, a conductive layer, and a second blackened layerin sequence; and patterning the first blackened layer, the conductivelayer, and the second blackened layer by using a same mask, and formingon front and rear surfaces of an EMI shielding layer a conductivepattern comprising the first and second blackened layers.

Still another aspect of the invention provides a manufacturing method ofan electromagnetic interference (EMI) shielding filter, the methodincluding the steps of: preparing a base film; forming on the base filma first blackened layer and a conductive layer; patterning the firstblackened layer and the conductive layer by using a same mask, andforming on the rear surface of an EMI shielding layer a conductivepattern comprising the first blackened layer; and forming a second,third, and fourth blackened layer for encompassing a front surface andboth side surfaces of the conductive pattern.

Another aspect of the invention provides a front filter of a plasmadisplay panel, in which the front filter includes a conductive patternfor shielding electromagnetic waves, and a base film for supporting theconductive pattern, and blacked layers are formed on a part of theconductive pattern.

Additional advantages, objects, and features of the invention will beset forth in part in the description which follows and in part willbecome apparent to those having ordinary skill in the art uponexamination of the following or may be learned from practice of theinvention. The objects and advantages of the invention may be realizedand attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in detail with reference to thefollowing drawings in which like reference numerals refer to likeelements wherein:

FIG. 1 is a perspective view of a related art three-electrode AC surfacedischarge plasma display panel (PDP);

FIG. 2 is a schematic perspective view of a PDP set including a PDP ofFIG. 1;

FIG. 3 is a cross-sectional view showing a vertical structure of a glasstype front filter and PDP of FIG. 2, respectively;

FIG. 4 is a cross-sectional view showing a vertical structure of a PDPto which a related art film type front filter is attached;

FIG. 5 is a plan view showing a detailed structure of a related artelectromagnetic interference (EMI) shielding filter of FIG. 3 and FIG.4;

FIG. 6 is a cross-sectional view of a related art EMI shielding filter,taken along line A-A′ in FIG. 5;

FIG. 7 is a cross-sectional view showing a structure of an EMI shieldingfilter according to a first embodiment of the present invention,

FIGS. 8A and 8B are cross-sectional views showing a step-by-stepprocedure for manufacturing an EMI shielding filter according to thepresent invention;

FIG. 9 is a cross-sectional view showing a structure of an EMI shieldingfilter according to a second embodiment of the present invention; and

FIGS. 10A through 10C are cross-sectional views showing a step-by-stepprocedure for manufacturing an EMI shielding filter according to thepresent invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following detailed description will present an electromagneticinterference (EMI) shielding filter and a manufacturing method thereofaccording to a preferred embodiment of the invention in reference to theaccompanying drawings.

FIG. 7 is a cross-sectional view showing a structure of an EMI shieldingfilter according to a first embodiment of the present invention. Asshown in FIG. 7, the EMI shielding filter includes an EMI shieldinglayer 83 formed of conductive meshes 84 and frames 86 for supporting theconductive meshes 84, and a base film 82 on which the EMI shieldinglayer 83 is formed.

The conductive meshes 84 of the EMI shielding layer 83 are positioned atan area where light (visible rays) from a display panel (e.g., a PDP) istransmitted, and secure transmittance and absorb electromagnetic wavesemitted from the display panel. The frames 86 encompasses outside of theconductive meshes 84 to support the conductive meshes 84 and to form adischarge path for absorbed electromagnetic waves. The EMI shieldinglayer 83 formed of the conductive meshes 84 and the frames 86 are madefrom metals including silver (Ag) or copper (Cu).

The base film 82 supports the EMI shielding layer 83.

Also, a blackened layer 88 is formed on the surface of the metallic EMIshielding layer 83 to prevent light reflection. More specifically, theblackened layer 88 includes a first blackened layer 88A formed on a rearsurface of the EMI shielding layer 83 to absorb a display light from thedisplay panel, and a second blackened layer 88B formed on a frontsurface of the EMI shielding layer 83 to absorb an externally incidentlight. Therefore, the blackened layer 88 is useful for preventing theexternal light reflection and display light reflection by the EMIshielding layer 83, and as a result thereof, contrast ratio can beimproved.

Here, the blackened layer 88 can be formed by oxidizing metals like Cuor Ni or oxidizing an alloy.

In addition, at least one of the first and second blackened layers 88Aand 88B can be formed by oxidizing the EMI shielding layer 83.

A manufacturing method of the EMI shielding filter with the abovestructure will be now explained.

As shown in FIG. 8A, a base film 82 is first prepared, and then thefirst blackened layer 88A, a conductive layer 85 and the secondblackened layer 88B are sequentially formed on the top of the base film82. Here, the conductive layer 85 is formed trough a deposition processlike a sputtering. The first and second blackened layers 88A and 88B areformed through a screen printing, compound thin film coating, orelectrochemical blackening process.

The second blackened layer 88B is coated with a photo-resist, and thephotoresist is patterned through a mask. In this manner, a photoresistpattern is formed on the frames and meshes. Using the photoresistpattern as a mask, the second blackened layer 88B, the conductive layer85, and the first blackened layer 88A are patterned in like manner.Hence, as shown in FIG. 8B, the first and second blackened layers 88Aand 88B are formed on the rear and front surfaces of the EMI shieldinglayer, that is on the rear and front surfaces of the conductive meshes84 and frames 86, respectively. Lastly, any photoresist patternsremaining on the second blackened layer 88B are removed through a stripprocess.

FIG. 9 is a cross-sectional view showing a structure of an EMI shieldingfilter according to a second embodiment of the present invention. Asshown in FIG. 9, the EMI shielding filter includes an EMI shieldinglayer 93 formed of conductive meshes 94 and frames 96 for supporting theconductive meshes 94, and a base film 92 on which the EMI shieldinglayer 83 is formed.

The conductive meshes 94 of the EMI shielding layer 93 are positioned atan area where light (visible rays) from a display panel (e.g., a PDP) istransmitted, and secure transmittance and absorb electromagnetic wavesemitted from the display panel. The frames 96 encompasses outside of theconductive meshes 94 to support the conductive meshes 94 and to form adischarge path for absorbed electromagnetic waves. The EMI shieldinglayer 93 formed of the conductive meshes 94 and the frames 96 are madefrom metals including silver (Ag) or copper (Cu).

The base film 92 supports the EMI shielding layer 93.

Also, a blackened layer 98 is formed on the surface of the metallic EMIshielding layer 93 to prevent light reflection. More specifically, theblackened layer 98 includes first through fourth blackened layers 98Athrough 98D that are formed on the front, rear and both side surfaces ofthe EMI shielding layer 93, respectively. The second blackened layer 98Bformed on the front surface of the EMI shielding layer 93 absorbs anexternally incident light, the first blackened layer 98A formed on therear surface of the EMI shielding layer 93 absorbs a display light fromthe display panel, and the third and fourth blackened layers 98C and 98Dformed on both sides of the EMI shielding layer 93 absorb the externallight and the display light, respectively. Therefore, the blackenedlayer 98 is useful for preventing the external light reflection anddisplay light reflection by the EMI shielding layer 93, and as a resultthereof, contrast ratio can be improved.

A manufacturing method of the EMI shielding filter with the abovestructure will be now explained.

As shown in FIG. 10A, a base film 92 is first prepared, and then thefirst blackened layer 98A, and a conductive layer 95 are sequentiallyformed on the top of the base film 92. Here, the conductive layer 95 isformed through a deposition process like a sputtering. The firstblackened layers 88A is formed through a screen printing or compoundthin film coating process.

The conductive layer 95 is coated with a photoresist, and thephotoresist is patterned through a mask. In this manner, a photoresistpattern is formed on the frames and meshes. Using the photoresistpattern as a mask, the conductive layer 95 and the first blackened layer98A ate patterned in like manner. Hence, as shown in FIG. 10B, the EMIshielding layer, that is, the conductive meshes 94 and frames 96, isformed on the base film 92, and the first blackened layer 98A is formedon the rear surfaces of the conductive meshes 94 and frames 96,respectively. Any photoresist patterns remaining on the conductivemeshes 94 and frames 96 are removed through a strip process.

Referring to FIG. 10C, after the first blackened layer 98A is formed,the second through fourth blackened layers 98B through 98D are formed onthe surface of the EMI shielding layer 93 formed of the conductivemeshes 94 and frames 96. The second through fourth blackened layers 98Bthrough 98D can be formed on the front and both side surfaces of theconductive meshes 94 and frames 96 through an electrochemicalblackening, e.g., electroless plating, or screen printing or compoundthin film coating process.

In conclusion, the EMI shielding filter and manufacturing method thereofcan be advantageously used for preventing external light reflection anddisplay light reflection by blackening the surface of the EMI shieldingfilter and thus, can improve contrast ratio of the display device.

While the invention has been shown and described with reference tocertain preferred embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims.

The foregoing embodiments and advantages are merely exemplary and arenot to be construed as limiting the present invention. The presentteaching can be readily applied to other types of apparatuses. Thedescription of the present invention is intended to be illustrative, andnot to limit the scope of the claims. Many alternatives, modifications,and variations will be apparent to those skilled in the art. In theclaims, means-plus-function clauses are intended to cover the structuresdescribed herein as performing the recited function and not onlystructural equivalents but also equivalent structures.

1. An electromagnetic interference (EMI) shielding filter, comprising: aconductive pattern for shielding electromagnetic waves; and blackenedlayers formed on a surface of the conductive pattern. 2-13. (canceled)